Mindray WATO EX-55, Service Manual

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The following is the pneumatic circuit diagram of the pneumatically-controlled module.
Proportional electromagnetic valve 10 controls inlet gas flow. Filter 8 filters drive gas again.
Regulator 9 regulates presssure inside the pneumatic circuit (approximately 0.2 MPa). “11” is
a flow sensor of differential pressure type which monitors gas flow in the drive gas circuit.
Mechanical overpressure valve 12 ensures that the pressure in the drive gas circuit does not
exceed safe pressure. It releases excess gas when gas pressure exceeds 11 kPa.. “17” is
expiratory valve. During expiration, gas inside the bellows is discharged from this valve.
The PEEP function is performed through expiratory valve. “16” is low-flow proportional
electromagnetic valve. When it opens, gas is bled from pneumatic resistor 18, forming
relatively stable pressure in the pneumatic circuit between “16” and “18”. Such pressure is
exerted on the membrane of expiratory valve 17 to form PEEP.
To prevent too high pressure inside the pneumatic circuit from injuring the patient and
damaging the equipment, safety valve 14, which is electromagnetic on-off valve, is placed
before the gas pathway of the expiratory valve. “15” is a pressure switch. When drive gas
pressure is less than 140 kPa, an alarm is triggered. “48” is a pressure sensor which monitors
the pressure at which the expiratory valve is closed. Pressure relief valve 51 ensures the tube
pressure after the expiratory valve is less than 10 cmH2O.